Tetravalent dengue vaccine

ABSTRACT

The invention provides a recombinant polypeptide comprising the EDIII domain of each of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 linked to the N-terminal of HBsAg.

FIELD OF THE INVENTION

The present invention relates to a recombinant dengue subunit vaccine against all the four serotypes-DENV-1, DENV-2, DENV-3, DENV-4 of Dengue. The present invention also relates to a recombinant VLP-based dengue quadrivalent vaccine candidate comprising tetravalent EDIII-T molecule and surface antigen of Hepatitis B virus (HBsAg). The present invention also relates to a process for the production of recombinant VLP (virus like particle)-based dengue quadrivalent vaccine candidate.

BACKGROUND OF THE INVENTION

Dengue disease caused by four antigenically distinct dengue viruses (DENVs) is a serious health concern in more than 150 countries of the world and especially in highly endemic countries like India. This disease has been on the rise since the last decade and has become a global public health threat because of lack of effective vaccine or antiviral therapies. Dengue disease is a global challenge for healthcare systems particularly during outbreaks, and millions of dollars are spent every year for vector control. An efficient and safe vaccine that is cost-effective could resolve the burden that dengue virus imposes on affected countries. Despite intensive efforts over the past three decades to develop a prophylactic vaccine for limiting the spread of disease, there is no licensed vaccine in the market as yet. Research groups/companies all over the world are undertaking efforts to develop an effective tetravalent vaccine against all serotypes of Dengue virus. Earlier most of the vaccines developed were based on live, attenuated, chimeric viruses and some of them are currently under clinical trials. However, due to limitations such as viral interference, the research focus has transitioned towards subunit vaccines particularly using the domain III of the envelope (E) protein of the dengue virus. Numerous patents/publications exploiting this domain have also been reported.

Though a live flavivirus based dengue vaccine has entered phase III clinical trials, problems due to viral interference have been reported. Viral interference arises presumably because of differences in replicative potential and immunogenicity of the four vaccine virus strains.

Non-replicative subunit vaccines have the potential to overcome the risk of viral interference associated with live virus vaccines [Swaminathan, Khanna, N. (2009), Dengue: Recent advances in biology and current status of translational research, Current Mol. Med. 9: 152-173]. Several approaches using recombinant DNA and protein based subunit vaccines are being explored. The majority of such recombinant subunit vaccines focus on the major envelope (E) protein. A number of evidences have further shown that many of the vaccine properties of the E protein are associated with domain III (EDIII).

DENV envelope domain III (EDIII) has been shown to be responsible for recognition of the host cell receptor and generation of neutralizing antibodies [Swaminathan, Khanna, N. (2009). Dengue: Recent advances in biology and current status of translational research, Current Mol. Med. 9: 152-173; Guzman, M. G. Hermida, L., Bernardo, L., Ramirez, R., Guillen, G. (2010). Domain II of the envelope protein as a dengue vaccine target]. Moreover, EDIII has been reported to have only a very low intrinsic potential for inducing cross-reactive anti-bodies [Simmons, M, Nelson, W. M, Wu, S. J., Hayes, C. G. (1998). Evaluation of the protective efficacy of a recombinant dengue envelope B domain fusion protein against dengue 2 virus infection in mice; Am. J. Trop. Med. Hyg. 58: 655-662; Simmons, M, Murphy, G. S., Hayes, C. G. (2001). Short report: anti-body responses of mice immunized with a tetravalent dengue recombinant protein subunit vaccine, Am. J. Trop. Med. Hyg. 65: 159-161]. These attributes make EDIII an excellent vaccine candidate. The efficacy of EDIII as a potential dengue vaccine antigen in the form of tetravalent protein has already been established by the inventors [Etemad, B., Batra, G., Raut, R., Dahiya, S., Khanam, S., Swaminathan,S., Khanna, N. (2008)].

Numerous patents/publications exploiting domain III of the envelope (E) protein of the dengue virus have been reported viz,

Suzarte, E., Gil, L., Valdés, I., Marcos, E., Lazo, L., Izquierdo, A., . . . & Hermida, L. (2015), International immunology, dxv011 discloses a novel tetravalent formulation combining the four aggregated domain III-capsid proteins from dengue viruses induces a functional immune response in mice and monkeys. This reference teaches a vaccine candidate against dengue virus based on two different viral regions, the domain III of the envelope protein and the capsid protein, wherein the tetravalent formulation of DIIIC proteins was used. The novel chimeric protein from dengue-2 virus (domain III-capsid (DIIIC-2)), when presented as aggregates incorporating oligodeoxynucleotides, induced antiviral and neutralizing antibodies, cellular immune response, and conferred significant protection to mice and monkeys. The remaining constructs were already obtained and properly characterized. Based on these evidences the present work was aimed at assessing the immune response in mice of the chimeric proteins DIIIC of each serotype, as monovalent and tetravalent formulations. The present inventors demonstrated the immunogenicity of each protein in terms of humoral and cell-mediated immunity, without antigen competition on the mixture forming the formulation tetra DIIIC. Accordingly, significant protection was afforded as measured by the limited viral load in the mouse encephalitis model. The assessment of the tetravalent formulation in non-human primates was also conducted. In this animal model, it was demonstrated that the formulation induced neutralizing antibodies and memory cell-mediated immune response with IFN-γ-secreting and cytotoxic capacity, regardless the route of immunization used. The tetravalent formulation of DIIIC proteins constitutes a promising vaccine candidate against dengue virus.

Zuest, R., Valdes, I., Skibinski, D., Lin, Y., Toh, Y. X, Chan, K, . . . & Fink, K. (2015), Vaccine 33(12),1474-1482 discloses the immunogenicity of a tetravalent formulation of a recombinant fusion protein consisting of E domain III and the capsid protein of dengue serotypes 1-4 (TetraDIIIC) to impart immunity against the dengue virus. E domain III is an epitope for efficient neutralizing antibodies while the capsid protein contains T cell epitopes. Besides combining B and T cell epitopes, Tetra DIIIC is highly immunogenic due to its aggregate form and a two-component adjuvant. Following previous studies assessing the monovalent DIIIC formulations, were addressed the quality and breadth of the T cell- and antibody response of Tetra DIIIC in mice. Tetra DIIIC induced a Th1-type response against all four DENV serotypes and dengue-specific antibodies were predominantly IgG1 and IgG2a and neutralizing, while the induction of neutralizing antibodies was dependent on IFN signaling. Importantly, the Th1 and IgG1/IgG2a profile of the DIIIC vaccine approach is similar to an efficient natural anti-dengue response.

Izquierdo, A., Garcia, A., Lazo, L., Gil, L., Marcos, E., Alvarez, M, & Guzmán, M. G. (2014), Archives of Virology, 159(10), 2597-2604 discloses a tetravalent dengue vaccine containing a mix of domain III-P64k and domain III-capsid proteins induces a protective response in mice. This reference teaches a vaccine candidate containing domain III of the dengue virus (type 1, 3 and 4) envelope protein fused to the P64k protein from Neisseria meningitidis and domain III of dengue virus type 2 (D2) was found to be immunogenic. Recombinant fusion proteins containing domain III of the dengue virus envelope protein fused to the P64k protein from Neisseria meningitidis and domain III of dengue virus type 2 (D2) fused to the capsid protein of this serotype were immunogenic and conferred protection in mice against lethal challenge in mice immunized with this tetravalent formulation were evaluated.

Live attenuated vaccines (LAVs), considered the most effective approach for dengue, have belied this expectation. Recent data from an efficacy trial of the most advanced LAV candidate showed an overall efficacy of 30%, with no efficacy for DENV-2. This necessitates serious exploration of alternate approaches to develop a dengue vaccine. VLP-based dengue quadrivalent vaccine candidate, ‘DSV⁴’, is an HBsAg-based VLP displaying all the four EDIIIs corresponding to the four serotypes of DENV developed.

Initially, as disclosed in Indian Patent No. 261749, a Tetravalent Domain III protein (rTDIII), a single chimeric polypeptide comprising domain III of all four serotypes of Dengue virus, Dengue-1, 2, 3 and 4, linked with each other through penta-glycine linkers, was codon-optimised for expression in E. coli.

An another Indian Patent application No. 1259/DEL/2007 discloses a recombinant envelop domain-III based tetravalent protein with and without secretory signal peptide eliciting protective immune responses against each of the four serotypes of dengue virus, DEN-1, DEN-2, DEN-3 and DEN-4, the said protein encoded by a polynucloeotide sequence codon optimized for expression in eukaryotic expression system.

Ability of Hepatitis B surface antigen (HBsAg) to serve as a platform for the presentation and display of foreign epitopes is illustrated well by the success of malarial vaccine candidate RTS,S. In order to increase the immunogenicity of EDIII-T, the inventors have explored whether HBsAg could serve well for its display. Therefore, EDIII-T was cloned in fusion with HBsAg and in a background of four expression cassettes of HBsAg in P. pastoris vector (FIG. 1A). This design of DSV⁴ is similar to that of RTS,S (Patent family: WO9310152 A1, MX9206574 A, EP0614465 A1, etc.), which displays malarial epitope on HBsAg VLPs.

The novelty of the present invention lies in the construct of EDIII-T with HBsAg and in a background of four expression cassettes of HBsAg in a vector. Thus, this design of EDIII-T and HBsAg (termed as “DSV⁴”), can be deemed novel. The inventiveness of the present invention lies in the fusion of the EDIII-T with the HBsAg to increase the immunogenicity of the expressed protein by serving as a platform for presentation and for the co-expressed HBsAg protein to assemble into VLPs. A single recombinant tetravalent domain (EDIII-T) is cloned in fusion with HBsAg and co-expressed with HBsAg to form DSV⁴ Virus Like Particles (VLPs). The subunit tetravalent vaccine DSV⁴ generates DENV serotype specific neutralizing antibodies and is effective against each of the 4 serotypes of Dengue.

The present invention has/is expected to have the following advantages over the existing proposed vaccines.

The Sanofi live attenuated vaccines currently under Phase-3 trial require three immunizations over an extended dosing schedule (0, 6 and 12) of 12 months to elicit balanced neutralizing antibody responses to all 4 serotypes, while the Glaxo Smith Kline (in Phase 1 trials) is aiming at—2 doses 28 days apart—type of dosing schedule and Takeda (completed Phase 2 trials) with two doses separated by only three months, immunization regime. Thus, with the preliminary data, the immunization schedule of the present vaccine would be shorter than the Sanofi under-trial vaccine. Further, the present vaccine comprises EDIII-T of all the 4 DENV serotypes and HBsAg as a single recombinant protein whereas all the other vaccine candidates in trial including Sanofi's live attenuated virus vaccines are a mix of four candidates corresponding to the four serotypes.

Further, the fusion of the recombinant EDIII-T with the HBsAg would result not only in the formation of VLPs and co-expression of the recombinant immunogenic protein and the Hepatitis B surface antigen but could provide protection/immunization against Hepatitis B along with dengue. This could lead to the development of a dual vaccine, providing simultaneous immunization against all the serotypes of Dengue as well as Hepatitis B.

OBJECTS OF THE INVENTION

An important object of the present invention is to provide a dengue subunit vaccine against all the four serotypes-DENV-1, DENV-2, DENV-3, and DENV-4.

Another object of the present invention is to provide a recombinant VLP-based dengue quadrivalent vaccine candidate, DSV4.

Yet another object of the present invention is to provide a recombinant VLP based dengue quadrivalent vaccine candidate, DSV4 which generates DENV serotype specific neutralizing antibodies against each of the 4 serotypes of Dengue, DENV-1, DENV-2, DENV-3 and DENV-4.

Still another object of the present invention is to provide a process for the production of recombinant VLP-based dengue quadrivalent vaccine candidate.

A further object of the invention is to provide an efficient and safe vaccination approach against all the four serotypes of the Dengue virus.

SUMMARY OF THE INVENTION

In a first aspect the invention provides a recombinant polypeptide comprising the EDIII domain of each of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 linked to the N-terminal of HBsAg.

In a further aspect the invention provides nucleic acid sequence encoding a recombinant protein comprising the EDIII domain of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 linked to the N-terminal of HBsAg.

In a further aspect the invention provides a host cell transformed or transfected with a nucleic acid of the invention, wherein the host cell expresses HBsAg.

In a further aspect the invention provides a bio-nanoparticle comprising the recombinant polypeptide of the invention.

In a further aspect the invention provides a method of producing a bio-nanoparticle comprising the recombinant polypeptide of the invention, comprising culturing the host cell of the invention under appropriate conditions and recovering the expressed recombinant protein or bio-nanoparticle.

In a further aspect the invention provides a vaccine comprising the recombinant polypeptide of the invention.

In a further aspect, the invention provides a vaccine comprising the bio-nanoparticle of the invention.

In a further aspect the invention provides a method of treating or preventing Dengue virus, comprising administering to a subject the recombinant polypeptide of the invention, the bio-nanoparticle of the invention or the vaccine of the invention.

In a further aspect the invention provides the recombinant polypeptide of the invention, the bio-nanoparticle of the invention or the vaccine of the invention for use in treating or preventing Dengue virus.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1: (A) Design of DSV⁴: EDIII-T consisting of four EDIIIs corresponding to the four DENVs linked through hexaglycyl linker was genetically fused with HBsAg (S) to encode for EDIII-T-HBsAg, which was cloned in vector carrying four expression cassettes of HBsAg. The recombinant plasmid was linearized with Bgl II and electroporated into P. pastoris cells to obtain a clone co-expressing EDIII-T-HBsAg and HBsAg.

(B) Methanol induction: Uninduced (U) and induced (I) biomass of selected clone was prepared by methanol induction and analysed for expression by silver staining and western blotting. Silver stained gel shows expression of both EDIII-T-HBsAg (˜72 kDa) and HBsAg (˜25 kDa) in induced sample. Western blot with EDIII specific mAb detects EDIII-T-HBsAg, and with HBsAg specific mAb detects both EDIII-T-HBsAg and HBsAg.

(C) Purification of DSV⁴: Three preps of purified DSV⁴ from induced biomass.

FIG. 2: (A) Gel filtration chromatography of DSV⁴: DSV⁴ eluted in void volume when subjected to gel filtration chromatography. Analysis of protein in void volume by silver staining indicates presence of both EDIII-T-HBsAg and HBsAg.

(B) CsCl ultracentrifugation: Co-migration of EDIII-T-HBsAg and HBsAg on ultracentrifugation on CsCl column.

(C) Electron microscopic view of DSV⁴ VLPs: 25-35 nm sized DSV⁴ VLPs as observed on negative staining under an electron microscope.

FIG. 3: (A) Source of EDIII sequence: Genotype of each DENV serotype from which corresponding EDIII aa sequence was derived.

(B) ELISA reactivity of DSV⁴ antiserum: Reactivity of pooled DSV⁴ antiserum against HBsAg, EDIII-1, EDIII-2, EDIII-3 and EDIII-4. Purple curve represents reactivity of un-immunized serum against DSV⁴.

(C) DSV⁴ generates balanced neutralizing titres: FACS-based neutralization titres of DSV⁴ antiserum against specified genotype(s) of each serotype.

(D) Genotype neutralization breadth with pooled sera

FIG. 4: (a) the amino acid sequence of the envelope domain III of DENV-1 (SEQ ID NO:1) and the encoding nucleic acid (SEQ ID NO:5);

(b) the amino acid sequence of the envelope domain III of DENV-2 (SEQ ID NO:2) and the encoding nucleic acid (SEQ ID NO:6);

(c) the amino acid sequence of the envelope domain III of DENV-3 (SEQ ID NO:3) and the encoding nucleic acid (SEQ ID NO:7);

(d) the amino acid sequence of the envelope domain III of DENV-4 (SEQ ID NO:4) and the encoding nucleic acid (SEQ ID NO:8);

(e) the amino acid sequence of the N-terminal of HBsAg (SEQ ID NO:9) and the encoding nucleic acid (SEQ ID NO:10);

(f) the amino acid sequence of a recombinant polypeptide of the invention comprising EDIII's from DENV-1, 2, 3 and 4 linked to the N-terminal of HBsAg (SEQ ID NO:11) and the encoding nucleic acid (SEQ ID NO:12), wherein the italicized nucleic acid and amino acid sequences are hexa-glycine linkers and the underlined nucleic acid and amino acid sequences are resulting from translation of KpnI restriction site. The EDIII's are sequentially order from N-terminus to C-terminus DNV-1, DNV-3, DNV-4 and DNV-2.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a dengue subunit vaccine against all the four serotypes-DENV-1, DENV-2, DENV-3, and DENV-4 serotypes of Dengue virus. The subunit vaccine comprises a recombinant protein comprising tetravalent EDIII-T and HBsAg. The present invention also relates to a subunit vaccine comprising VLP-based quadrivalent vaccine candidate for the prevention of dengue disease against all the four serotypes of DENV.

In one aspect the invention provides a nucleic acid sequence encoding a recombinant protein comprising the EDIII domain of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 linked in frame to the N-terminal of HBsAg. The nucleotide sequences encoding each of the EDIII domains of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 can be linked with the N-terminus of HBsAg in any sequential order.

Preferably, the nucleic acid sequence encodes EDIII domains of each of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4, which have the amino acid sequences of SEQ ID NO's: 1, 2, 3 and 4 respectively. Preferably, the nucleic acid sequence encoding each of the EDIII domains of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 is SEQ ID NO's: 5, 6, 7 and 8 respectively.

Preferably, the nucleic acid sequence encodes a HBsAg having the amino acid sequence of SEQ ID NO:9. Preferably, the nucleic acid sequence encoding HBsAg is SEQ ID NO:10.

In one embodiment the nucleic acid sequence comprises each of the nucleotide sequences SEQ ID NO's: 5, 6, 7 and 8 linked in frame with the N-terminus of SEQ ID NO: 10. The nucleotide sequences SEQ ID NO's: 5, 6, 7 and 8 can be linked with the N-terminus of SEQ ID NO: 10 in any sequential order.

Preferably, the nucleic acid sequence encodes a linker that links each of the EDIII domains of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4. Preferably, the nucleic acid encodes a flexible linker, most preferably a hexa-glycine linker. Preferably, the nucleic acid sequence encodes a linker that links the EDIII domains of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 to the N-terminal of HBsAg. Preferably, the nucleic acid encodes a flexible linker, most preferably a hexa-glycine linker.

Preferably, the nucleic acid sequence encodes a recombinant polypeptide having the amino acid sequence of SEQ ID NO: 11. Preferably, the nucleic acid sequence encoding the recombinant polypeptide is the nucleic acid sequence of SEQ ID NO:12.

In one embodiment the nucleic acid sequence is codon optimized for expression in yeast, preferably for expression in P. pastoris. In one embodiment the nucleic acid is an expression vector.

In one aspect the invention relates to a host cell transformed or transfected with a nucleic acid of the invention, wherein the host cell expresses HBsAg. In one embodiment the host cell is transformed or transfected with a nucleic acid sequence that encodes HBsAg. Preferably, the host cell is transformed or transfected with 1, 2, 3, 4 or more nucleic acid sequences expressing HBsAg. In one embodiment the host cell is a yeast. Most preferably, the host cell is P. pastoris.

In one aspect the invention provides a recombinant polypeptide comprising the EDIII domain of each of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 linked to the N-terminal of HBsAg. The amino acid sequences encoding each of the EDIII domains of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 can be linked with the N-terminus of HBsAg in any sequential order. Preferably, EDIII domains of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 are fused sequentially, N-terminal to C-terminal, in the sequence DENV-1, DENV-3, DENV-4 and DENV-2

Preferably, the amino acid sequence of the EDIII domains of each of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 is SEQ ID NO's: 1, 2, 3 and 4 respectively. Preferably, the N-terminal of HBsAg has the polypeptide sequence of SEQ ID NO:9. Preferably, the recombinant polypeptide comprises each of the amino acid sequences SEQ ID NO's: 1, 2, 3 and 4 linked to the N-terminus of SEQ ID NO:9. The amino acid sequences SEQ ID NO's: 1, 2, 3 and 4 can be linked with the N-terminus of SEQ ID NO: 9 in any sequential order. Preferably, the recombinant polypeptide comprises the amino acid sequences SEQ ID NO's:1, 2, 3, and 4 sequentially, N-terminal to C-terminal, in the sequence SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 4 and SEQ ID NO:2.

Preferably, the EDIII domains of each of Dengue virus serotype DENV-1, DENV-2, DENV-3, and DENV-4 are linked by a linker, preferably a flexible linker, most preferably a hexa-glycine linker. Preferably, the EDIII domains are linked to the N-terminal of HBsAg by a linker, preferably a flexible linker, most preferably a hexa-glycine linker.

In one aspect the recombinant polypeptide has the amino acid sequence of SEQ ID NO: 11.

The transformed or transfected host cells of the invention synthesises both HBsAg and the recombinant polypeptide of the invention. The inventors have shown that these two polypeptides spontaneously co-assemble into bio-nanoparticle. In one aspect the invention includes bio-nanoparticle comprising HBsAg and the recombinant polypeptide of the invention of the invention.

In one aspect the invention provides a method of preparing a recombinant protein or bio-nanoparticle comprising culturing the host cell of the invention under appropriate conditions and recovering the expressed recombinant protein or bio-nanoparticle.

In one aspect, the invention relates to a vaccine comprising the recombinant polypeptide or the bio-nanoparticles of the invention. Preferably, the vaccine comprises the recombinant polypeptide or the bio-nanoparticle of the invention in a pharmaceutically acceptable carrier or suitable diluent.

In one aspect, the invention provides a method of treating or preventing Dengue virus, comprising administering to a subject a recombinant protein, a bio-nanoparticle or a vaccine of the invention. In one embodiment the Dengue virus is serotype DENV-1, DENV-2, DENV-3, or DENV-4.

The tetravalent EDIII-based molecule, EDIII-T, was developed, which was designed to contain all the four EDIIIs linked together through flexible glycyl linkers as depicted in FIG. 1A. EDIII-T was expressed in Pichia pastoris, purified and was found to be immunogenic in mice. The construction of the EDIII-T molecule is provided in the Indian Patent No. 261749.

The ability of surface antigen of Hepatitis B virus (HBsAg) to serve as a platform for the presentation and display of foreign epitopes is illustrated well by the success of malarial vaccine candidate RTS,S in the Patent Application No. WO 93/10152.

The present invention explores the possibilities whether HBsAg could serve to increase the immunogenicity of EDIII-T. Therefore, EDIII-T was cloned in fusion with HBsAg and in a background of four expression cassettes of HBsAg in P. pastoris vector as depicted in FIG. 1A. This design of EDIII-T and HBsAg is termed as “DSV⁴” and is similar to that of RTS,S in the Patent application no. WO9310152 which displays malarial epitope on HBsAg VLPs.

The recombinant plasmid was electroporated in P. pastoris and the colonies were screened for the co-expression of EDIII-T-HBsAg and HBsAg proteins by methanol induction of clones. One of the positive clones co-expressing the two proteins as shown in FIG. 1B, was selected for further study. Induced biomass was lysed and the proteins associated with the membrane were extracted and subjected to diafiltration through 300 kDa membrane. This step was designed to allow enrichment of large sized protein considering that the two co-expressed proteins assemble into DSV⁴ VLPs. The retentate was purified through phenyl 600M resin with high purity as depicted in FIG. 1C.

Ability of the co-expressed proteins to assemble into VLPs was evaluated through gel filtration as shown in FIG. 2A, CsCl Ultra-centrifugation as shown in FIG. 2B and electron microscopy as shown in FIG. 2C. It was observed that both the protein components of DSV⁴ eluted together in the void volume during gel filtration as shown in FIG. 2A and co-migrated during CsCl ultra-centrifugation as shown in FIG. 2B. On visualization under electron microscope, they were observed to assemble into 25-35 nm VLPs as shown in FIG. 2C.

The conformational integrity of EDIII of all four DENVs in DSV⁴ VLPs was evaluated through recognition of critical EDIII epitopes by well characterized mAbs in sandwich ELISA format.

Capability of these VLPs to mount a strong immune response against the four DENV serotypes was evaluated by immunization in BALB/c mice as shown in FIG. 3. Purified DSV⁴ VLPs were immunized (20 μg/500 μg Al as alhydrogel/100 μl in PBS) in a group of six BALB/c mice intraperitoneally on days 0, 30 and 90. Terminal bleed was taken on day 100 and analysed for response against DSV⁴ by ELISA. Sera from positive responders were pooled and characterized for the presence of antibodies against all its five components namely EDIII-1, EDIII-2, EDIII-3, EDIII-4 and HBsAg (FIG. 3B). It was observed that a strong immune response was generated against all of them. It was essential to determine whether anti-dengue response was capable of neutralizing the four DENVs. Therefore, the pooled serum was evaluated for its neutralization capacity through FACS-based assay and it was observed that DSV⁴-antiserum was indeed capable of neutralizing all four DENVs (FIG. 3C). FIG. 3A illustrates the design of DSV⁴ and the strain from which corresponding EDIII aa sequences were acquired. FIG. 3C illustrates the neutralization titre of DSV⁴-antiserum against the four DENVs (of specified strain) and strains of two additional genotypes of DENV-3. It is evident that DENV-2, -3 and -4 genotypes used in neutralization assay varied from the genotypes from which EDIII sequence was acquired, and it did not adversely affect the neutralization capability of DSV⁴ antiserum, indicating the high strength of the generated immune response. Moreover, the overall response against the various genotypes also appeared to be balanced, highlighting the candidacy of DSV⁴ as a potential dengue vaccine as depicted in FIG. 3D. DSV4 appeared to be efficacious to comparable extent with various adjuvants evaluated (FIG. 3D)

The present invention is described with reference to the following examples, which are included merely to illustrate and demonstrate the invention. These specific examples should not be construed to limit the scope of the invention in any way.

EXAMPLE 1 Construction of Recombinant VLP-Based Dengue Quadrivalent Vaccine Candidate

EDIII-T was cloned in fusion with HBsAg and in a background of four expression cassettes of HBsAg in P. pastoris vector as depicted in FIG. 1A. This design of EDIII-T and HBsAg is termed as “DSV⁴”. The recombinant plasmid was electroporated in P. pastoris and the colonies were screened for the co-expression of EDIII-T-HBsAg and HBsAg proteins by methanol induction of clones.

EXAMPLE 2 Characterization of Dengue Quadrivalent Vaccine Candidate-DSV⁴

One of the positive clones co-expressing the two proteins as shown in FIG. 1B, was selected for further study. Induced biomass was lysed and the proteins associated with the membrane were extracted and subjected to diafiltration through 300 kDa membrane. This step was designed to allow enrichment of large sized protein considering that the two co-expressed proteins assemble into DSV⁴ VLPs. The retentate was purified through phenyl 600M resin with high purity as depicted in FIG. 1C.

EXAMPLE 3 Identification and Characterization of VLPs

Ability of the co-expressed proteins to assemble into VLPs was evaluated through gel filtration as shown in FIG. 2A, CsCl Ultra-centrifugation as shown in FIG. 2B and electron microscopy as shown in FIG. 2C. It was observed that both the protein components of DSV⁴ eluted together in the void volume during gel filtration as shown in FIG. 2A and co-migrated during CsCl ultra-centrifugation as shown in FIG. 2B. On visualization under electron microscope, they were observed to assemble into 25-35 nm VLPs as shown in FIG. 2C.

EXAMPLE 4 Evaluation of Conformational Integrity of All Four DENVs in DSV⁴ VLPs by mAbs

The conformational integrity of EDIII of all four DENVs in DSV⁴ VLPs was evaluated through recognition of critical EDIII epitopes by well characterized mAbs in sandwich ELISA format. Dengue specific mAbs were coated in microtiter wells and DSV⁴ VLPs were added. Bound VLPs were revealed through peroxidase labelled anti-HBsAg Hepnostika. Most of these mAbs were against A-strand and lateral ridge region of EDIII, which are believed to be essential in generating a strong neutralizing immune response. ELISA reactivity of DSV⁴ by 21 dengue mAbs (EDIII and non-EDIII specific mAbs) is illustrated in Table 1 and the results indicate that EDIII epitopes of all four DENVs are intact in DSV⁴ VLPs.

TABLE 1 List of EDIII-specific mAbs, regions recognized by them and their reactivity with ‘DSV⁴’ VLPs (in terms of ELISA OD) Anti-EDIII Strongly ELISA mAbs neutralizes Region specificity OD E103 DENV-1 L.R-BC loop 3.96 3H5 DENV-2 A.S and BC loop (L.R) 0.77  70 A.S 0.48 106 A.S 0.51 104 C strand/CC′ loop 0.52 8A1 DENV-3 LR-N terminus of 1.30 A.S, FG loop E51 236 L.R 1.84 E51 202 L.R 3.90 E88 DENV-4 BC and DE loop (L.R) 0.53 E76 DENV-4, -2 N terminal A.S, CC′ 0.51 loop, B, D and G strands E106 DENV-1, -4 A.S and L.R 3.60 E113 DENV-1, -2, -4 L.R 1.20 h-2J20 DENV-1, -3 2.50 E61 DENV-1, -2, -3, -4 A.S and G strand 0.71 E77 A.S, BC loop and G strand 0.81 Non-EDIII ELISA mAbs Ab type Region specificity OD h-2K2 Complex prM 0.06 4G2 Fusion Loop 0.05 h-1M7 0.06 h-DVC23.13 0.05 3H4 0.05 h-1N5 0.05

EXAMPLE 5 Immunization of Mice by Purified DSV⁴ VLPs

Capability of these VLPs to mount a strong immune response against the four DENV serotypes was evaluated by immunization in BALB/c mice as shown in FIG. 3. Purified DSV⁴ VLPs were immunized (20 μg/500 μg Al as alhydrogel/100 μl in PBS) in a group of six BALB/c mice intraperitoneally on days 0, 30 and 90. Terminal bleed was taken on day 100 and analysed for response against DSV⁴ by ELISA. Sera from positive responders were pooled and characterized for the presence of antibodies against all its five components namely EDIII-1, EDIII-2, EDIII-3, EDIII-4 and HBsAg as depicted in FIG. 3B and further Genotype neutralization breadth of DSV⁴ antisera generated with various adjuvants was determined as depicted in FIG. 3D

Immune Response

It was observed that a strong immune response was generated against all of the five components namely EDIII-1, EDIII-2, EDIII-3, EDIII-4 and HBsAg. It was essential to determine whether anti-dengue response was capable of neutralizing the four DENVs. Therefore, the pooled serum was evaluated for its neutralization capacity through FACS-based assay and it was observed that DSV⁴-antiserum was indeed capable of neutralizing all four DENVs as shown in FIG. 3C which illustrates the neutralization titre of DSV⁴-antiserum against the four WHO reference strains DENVs and strains of two additional genotypes of DENV-3. It is evident that DENV-2, -3 and -4 genotypes used in neutralization assay varied from the genotypes from which EDIII sequence was acquired, and it did not adversely affect the neutralization capability of DSV⁴ antiserum, indicating the high strength of the generated immune response. Moreover, the overall response against the various serotypes also appeared to be balanced, highlighting the candidacy of DSV⁴ as a potential dengue vaccine. Table 2 below illustrates FNT post depletion on EDIII-3-MBP eliciting serotype specific neutralizing Abs.

TABLE 2 FNT post depletion on EDIII-3-MBP elicits serotype specific neutralizing Abs Sera depleted FNT₈₀-Vero on DENV-1 DENV-2 DENV-3 DENV-4 Sera 1: MBP 714 678 2259 415 Depletion of EDIII- 1278 581 288 449 DENV-3 Abs 3-MSP Sera 2: MBP nd 775 1022 nd Depletion of EDIII- nd 78 975 nd DENV-2 Abs 2-MSP

The Invention Also Includes the Following Specific Aspects:

-   Aspect 1. A recombinant VLP-based dengue quadrivalent vaccine     candidate comprising a tetravalent EDIII-T molecule and the surface     antigen of Hepatitis B virus (HBsAg). -   Aspect 2. A recombinant VLP-based dengue quadrivalent vaccine     candidate designated DSV⁴. -   Aspect 3. The recombinant VLP-based dengue quadrivalent vaccine     candidate, DSV⁴, wherein the tetravalent EDIII molecule comprises     EDIII of DENV-1, DENV-2, DENV-3, and DENV-4. -   Aspect 4. The recombinant VLP based dengue quadivalent vaccine     candidate as recited in aspect 2 of the invention, wherein DSV⁴     generates DENV serotype specific neutralizing antibodies against     DENV-1, DENV-2, DENV-3 and DENV-4. -   Aspect 5. A process for the production of recombinant VLP-based     dengue quadrivalent vaccine candidate as claimed in claim 1     comprises the steps of:     -   i) cloning of EDIII-T in fusion with HBsAg in a recombinant         construct carrying four expression cassettes of HBsAg;     -   ii) electroporation of recombinant plasmid into Pichia pastoris         cells to obtain a clone co-expressing EDIII-T-HBsAg and HBsAg;     -   iii) screening for the co-expression of EDIII-T-HBsAg and HBsAg         proteins;     -   iv) analyzing the expression of EDIII-T-HBsAg and HBsAg proteins         by silver staining and western blotting;     -   v) lysis of the induced biomass;     -   vi) extraction of the proteins associated with the membrane and         subjected to diafiltration;     -   vii) purification of DSV⁴ -   Aspect 6. The process as recited in aspect 5, wherein the screening     in step (iii) is done by methanol induction of clones. -   Aspect 7. A dengue subunit vaccine comprising a recombinant     VLP-based dengue quadrivalent vaccine candidate as recited in aspect     1. -   Aspect 8. The dengue subunit vaccine as recited in aspect 7, wherein     said vaccine is active against DENV-1, DENV-2, DENV-3, and DENV-4     serotypes of Dengue virus. -   Aspect 9. The dengue subunit vaccine as recited in aspect 8 wherein     said vaccine can be administered intraperitoneally or     intramuscularly. -   Aspect 10. A recombinant VLP-based dengue quadrivalent vaccine     candidate for use as a dengue subunit vaccine candidate comprising     of tetravalent EDIII-T molecule and the surface antigen of Hepatitis     B virus (HBsAg). 

1.-9. (canceled)
 10. A tetravalent dengue vaccine comprising a virus like particle (VLP) comprising: a) a recombinant polypeptide comprising an EDIII domain of each of Dengue virus serotypes DENV-1, DENV-2, DENV-3, and DENV-4, linked to N-terminal of an HBsAg polypeptide, as depicted below: EDIII-1 - - - EDIII-3 - - - EDIII-4 - - - EDIII-2 - - - HBsAg; wherein the dotted line is a linker; and wherein the amino acid sequence of the EDIII domains of each of Dengue virus serotypes DENV-1, DENV-2, DENV-3, and DENV-4 is SEQ ID NO's 1, 2, 3 and 4, respectively; and b) 4 units of an HBsAg polypeptide.
 11. A method of eliciting neutralizing antibody titer against each of the four dengue virus serotypes DENV-1, DENV-2, DENV-3 and DENV-4 in a subject in need thereof comprising administering to the subject the tetravalent dengue vaccine of claim
 1. 12. A method of treating or preventing dengue virus infection comprising administering to a subject the tetravalent dengue vaccine of claim
 1. 13. The tetravalent dengue virus vaccine of claim 1 for use in eliciting neutralizing antibody titer against each of the four dengue virus serotypes DENV-1, DENV-2, DENV-3 and DENV-4.
 14. The tetravalent dengue virus vaccine of claim 1 for use in treating or preventing dengue virus infection. 